1. Field of the Invention
The present invention relates generally to sound recording and reproduction systems. More particularly, the present invention relates to local performance simulation.
2. Discussion of the Related Art
Sound recording and reproduction has long been the subject of research, development and debate. Conventional stereophonic practices create a musical environment for the listener by including recording environment information, specifically early reflections and reverberation. Recording engineers therefore pay close attention to the recording hall and the location of the microphones when they record ensembles. When the original recording has inadequate environment information, such information is typically added artificially through electronic reverb boxes and ambience synthesizers. Artificial addition is essential when the original recording is made electronically or by tight-miking techniques.
The value of replacing recording environment effects with the actual effects of the listing environment, therefore, have largely gone overlooked. There are many circumstances, however, in which it is quite desirable to simulate a “local performance.” For example, there is a small but significant market of classical music connoisseurs who would greatly value the experience of a string quartet playing in the comfort of their own homes. Another benefit of local performance simulation is the possibility of elimination of intermodulation (IM) distortion between the tones of different instruments. Because the tones of a musical instrument tend to be harmonic, local performance simulation would limit distortion to harmonic distortion only, causing only a slight change in coloration for the instrument.
It is also desirable to provide the ability to highlight a particular musical instrument in an ensemble for educational purposes. Similarly, local performance simulation would allow the tone color of each instrument to be varied to taste. For instance, when listening to a simulated quartet, the listener could elect to give the second violin a darker tone color to exaggerate the difference between it and the first violin. There is also a need to individually shut off any instrument of the ensemble to provide a “music-minus-n” system. The local performance technique would allow the performer to feel that the other musicians of the ensemble are with her and around her, in the same listening environment. Furthermore, because each instrument would be recorded separately, editing of recordings and processing of individual voices would be facilitated. Errors by one musician could be corrected without the participation of the other musicians. It is also desirable to optimize loudspeakers for their particular functions. This would eliminate the present need, for example, for a large low-frequency driver (woofer) in the system that is dedicated to a flute. Dedicating loudspeaker systems would therefore control the cost of multi-channel ensembles.
Present stereophonic practice sometimes attempts to localize sound images, but localization is psychoacoustically fragile. This means that present audio imaging approaches depend on the loudspeakers, listening environment, and listener position used by the ultimate consumer. Adding to the difficulty is the fact that the principle function of stereo is to de-localize the sounds from the loudspeaker positions themselves and to provide a broadened image. In other words, stereophonic recording by definition attempts to bring the listener into the recording environment instead of bringing the musical performance into the listening environment. Furthermore, conventional stereophonic sound reproduction and contemporary surround sound techniques require the listener to be in a particular place or area. It is thus desirable to provide a sound recording and reproduction system with accurate imaging capability. This capability would allow the listener to perceive the individual instruments or voices to be spatially compact, and well-localized in azimuth, elevation and distance. Furthermore, it would be desirable to allow the listener to walk entirely around the synthesized performing ensemble.